The present invention provides an improved system for generating in the earth's surface seismic signals that can be used in geophysical exploration.
Geophysical exploration, or more precisely seismic exploration, involves the introduction of energy into the earth. Energy waves generated at the earth's surface travel through the earth and when an energy wave encounters a strata which has a different velocity or density a small portion of the energy wave is reflected back which can be detected at the earth's surface. The reflected signals can be analyzed to estimate the shape, composition, depth and size of various strata within the earth and this information is employed in predicting where oil, gas or other valuable minerals may be located.
Seismic wave producing energy is induced into the earth surface for purposes of conducting seismic exploration in two basic formats, that is, compression waves (sometimes known as P-waves) and orthogonal shear waves (sometimes known as S1 and S2 type waves). Simply stated, compressional waves are typically generated by oscillating or vibrating weight along a vertical axis to the earth's surface whereas shear waves are typically generated by oscillating or vibrating weight along an axis that is inclined from the vertical.
For background information relating to seismic signal generating systems, reference may be had to the following previously issued United States patents:
______________________________________ U.S. Pat. No. INVENTOR TITLE ______________________________________ 5,666,328 Crowell et al Three Axis Seismic Vibrator 5,694,375 Woodall Ultra-Broadband Hydrophone 5,703,833 Allen One Step Inversion/Separation Scheme Using A Plurality Of Vibrator Sources 5,710,720 Algrain et al Phase Lock Loop Based System and Method For Decomposing and Tracking Decomposed Frequency Components Of A Signal, With Application To Vibration Compensation System 5,717,170 Anstey Swinging-Weight Vibrator For Seismic Exploration ______________________________________
The United States patent references cited in U.S. Pat. No. 5,666,328 contain additional background information relating to the subject of this disclosure.